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NASA Telescope Passed Complex Math Test so 19 Mirrors Work as One

08.24.07

Scientists and engineers have successfully created and tested a set of algorithms, or software programs with complex math-based instructions, that will enable 19 mirrors of NASA's powerful James Webb Space Telescope to function as one very sensitive telescope.

Image right: Engineers at Ball Aerospace test the Wavefront Sensing and Control testbed to ensure that the 18 primary mirror segments and one secondary mirror on JWST work as one. The test is performed on a 1/6 scale model of the JWST mirrors. Click image for Quicktime video. Credit: NASA/Northrop Grumman/Ball Aerospace

After its launch in 2013, when the Webb Telescope is exploring the universe from its observation point about one million miles from Earth, scientists back home need to be able to move its 18 primary mirror segments plus the secondary mirror to make them work as one big telescope. As a result of creating and testing nine algorithms, they can do that now. The process that uses the 9 algorithms is called "Wavefront Sensing and Control" or WFSC. The WFSC system can compute the position of each of the 19 mirrors, and then adjust each one if it is needed.

The James Webb Telescope's 18 primary mirror segments cover a combined total area of 25 square meters (approx. 30 square yards) and a diameter of 6.5 meters (approx. 21 feet). "It's critical that all 18 mirror segments be aligned in position so that they act as one smooth surface, and the secondary mirror be place exactly right," said Bill Hayden, Systems Engineer at NASA Goddard Space Flight Center, Greenbelt, Md. "This will allow scientists to clearly focus on very dim objects that we can't see now."

The WFSC system is put to work when the telescope takes images of a star. It then processes the images through the mathematical algorithms that calculate what mirror adjustments are needed. The mirrors are then moved into the proper place to help the telescope make clear images of an object like a faraway galaxy.

Image left: Through a process called "Wavefront Sensing and Control," or WFSC,
software aboard the observatory will compute the optimum position of each of the 18 primary mirrors and the one secondary mirror, and then adjust the positions, if necessary. Shown is a 1/6 model of the JWST mirrors that is used to test WFSC. Credit: NASA/Northrop Grumman/Ball Aerospace

Recently, a team of engineers from Ball Aerospace & Technologies Corp., Boulder, Colo. and NASA successfully tested the algorithms proving they are ready to work on the Webb Telescope in space. The algorithms were tested on a detailed scale model of the space telescope and through computer simulations.

"This major technological accomplishment, which built on the technological legacy of software algorithms used to fix the Hubble Space Telescope and align the Keck telescope, is a major step forward in the development of JWST. This achievement was the result of great teamwork between Ball Aerospace, NASA Goddard Space Flight Center, and the Jet Propulsion Laboratory," said John Mather, Senior Project Scientist on the Webb telescope at Goddard and the 2006 winner of the Nobel Prize in Physics.

Image right: Artist's conception of JWST in space. Credit: NASA

"The same technological ingenuity Ball Aerospace applied to correcting the Hubble Space Telescope’s primary mirror in 1993 is being applied to advancing the optics for the JWST observatory," said David L. Taylor, president and chief executive officer of Ball Aerospace & Technologies Corp.

The Webb Telescope is designed to study light from objects that formed in the beginning of the universe.